Method and mechanism for govern



G. SCHMIDT Aug. 24, 193 7.

Re. 20,487 METHOD AND MECHANISM FOR GOVERNING Romwme BODIES 5Sheets-Sheet l Original Filed June 5, 1930 AT OR EY G. SCHMIDT Re.20,487

METHOD AND MECHANISM FOR GOVERNING ROTATING BODIES ul- 9 1 4 2 u AOriginal Filed June 5, 1930 3 Sheets-Sheet 2 llllnlll ula ATTORNEY IAug. 24, 1937. v G, scHmD'r Re. 20,487

METHOD AND MECHANISM FOR GOVERNING ROTATING BODIES I Oriitinal FiledJune 5. 1930 3 Sheets-sheaf. 3

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Reissued Aug. 24, 1937 PATENT OFFICE METHOD AND MECHANISM FOR GOVERN-ING ROTATING BODIES Gra'yson Schmidt, West Point, N. Y., assignor, bydirect and mesne assignments,-to United Aircraft Corporation, EastHartford, Conn., a corporation of Delaware Original No. 2,003,558, datedJune 4, 1935, Serial No. 459,408, June 5, 1930.

Renewed August 30,

1934. Application for reissue June 3, 1931,

Serial No. 146,323

v11 Claims. (Cl. 6097) The invention relates to a novel and usefulmethod and mechanism for controlling the angular velocity of a rotatingbody or bodies. More particularly, the invention relates to such a meth-0d and mechanism for controlling a motor or plurality'of motors andmaintaining them in synchronous rotation with a master motor or otherstandard rotating member.

Objects and advantages of the invention will be set forth in parthereinafterand in part will be obvious herefrom, or may be learned bypractice with the invention; the same being realized and attained bymeans of the instrumentalities and combinations pointed out in-the'appended claims.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements herein shown and described.

, The accompanying drawings, referred to herein and constituting a parthereof, illustrate one embodiment of the invention, and together withthe description, serve to explain the principles of the invention.

Of the drawings:'-

Fig. 1 is a partially diagrammatic or schematic showing in plan of "apreferred embodiment of the invention, showing its application to themotors of a tri-'-motor airplane;

Fig. 2 is a vertical transverse section of a unit synchronizing device;

Fig. 3 is a top plan of the mechanism shown in Fig. 2;

of a unitsynchronizing device;

method and mechanism for controlling or govern-, ing the angularvelocity or rotation of a rotating body or bodies, such asinternal-combustion motors, turbines, or any other mechanisms which haverotary motion or a motlonwhich can be converted into rotation for thepurposes of such control. The invention is further directed to a 50novel and useful method and mechanism for in- Fig. 5 is a transversevertical section of a varidicatirig the variations in angular velocitybetween two rotating bodies.

The novel method of the invention broadly comprises detecting anddetermining or measuring the differences between the rotary speed of amaster or standard rotating body and that of the body or bodies to becontrolled, and automatically changing the rotary speed of the latter soas to eliminate such differences.

One fundamental object of the invention is to provide a method and meansfor accurately determining the actual differences in rotaryvelocity oftwo rotating bodies and, if desired, indicating such diflerencesvisually or otherwise, as

well as utilizing the determined differences for automatic governing ofsaid body or bodies.

The invention finds an extensive field of present usefulness in thecontrol and automatic synchronization of the motors of multi-motoredmachines such as airplanesand motor boats,

although it .will be understood that the principles of the invention arebroadly applicable to the control of' any rotating body or bodies. Onenotably useful and exemplary embodiment of the invention is illustratedin its application to av multi-motored airplane. Most of the largermodern airplanes have two or -more internal-combustion motors, thenumber of such motors sometimes being. as great as twelve in morerecently developed planes. In the piloting of multimotored airplanes, itis veryimportant that the different motors rotate in synchronism, i. e.,at Fig. 4 is an enlarged detail of the controlrack the same R. P. M., sothat all propellers will exert the same driving force on the plane andproper flying balancecan be maintained. For

example, in a tri-motored plane it is essentialthat the two outlyingmotors rotate at the same angular velocityor R. P. M., during normalflyin conditions on a. straight course, or otherwise there will be ,alateral turning moment about the lagging motor.

Present methods of maintaining a plurality of motors, such as airplanemotors, in synchronism are very crude and unsatisfactory. In manyinstances the pilot roughly tunes the motors by.

car, while at best the tuning is done by observing different tachometerswhich record the actual -R. P. M. of the respective motors and manuallycontrolling the respective motor throttles in ac- I cordan'ce with thediiferences in tachometer readings. Neither of these methods issatisfactory;

even for a 'bior tri-motor plane, and in planes with greater numbers ofmotors, accurate motor synchronization by such methods is virtually im-5 possible.

By virtue of the present invention it is possible to automaticallymaintain any number of motors in synchronized rotation, either at thesame R. P. M., or at any selectively predetermined and 10 variable ratioof angular velocities.

or motors to be governed are preferably maintained in synchronousrotation with a standard or master motor, which may itself be one of thedriving motors or a separate control motor alone,

15 as desired. In the tri-motor plane, for example, the outlying orright and left motors may be governed by the rotation of the central,motor so as to rotate at the same or a predeterminately proportional R.P. M., although this arrangement 20 is merely illustrative and by nomeans fixed or essential.

The invention further provides a method and means for varying theangular velocity between a given motor and the master motor and/or 25other motors being controlled thereby. For exar'hple,'in a tri-motorplane it is frequently desirable or necessary to drive one oftheoutlying motors at a different absolute R. P. M. from that a of theother two, which two may themselves differ in actual velocity, while atthe same time all three motors are maintained in predetermined ratios ofangular velocity. The action of the tri-motor' plane in making a bankedturn is illustrative. In banking to turn to the'left, for instance, theleft wing drops and forms the pivot, so that it is desirable to drivethe left or inner motor at a lower speed while the speed of the right orouter motorshould be correspondingly accelerated. By virtue of theinvention, it is 40 possible to instantly vary the actual speeds of oneor more of the motors as desired while maintaining all three in thedesired predetermned ratio of velocities.

The present preferred mechanism embodying 45 the invention comprises adevice which is responsive to the actual differences in the rotaryvelocities of a master motor and the motor to be controlled and movesproportionately to said differences. The movement of the device isutilized to vary the rotation of the body or motor being controlled soas to bring it into synchronous rotation with the master motor and thuseliminate these differences in R. P. M.

Preferably, a master control shaft driven by or connected to rotateproportionately to the master motor, and a shaft driven by or rotatingproportionately to the motor to be governed are connected bydifferential gearing. The housing or other portion of the differentialgearing which normally idles in mesh with the driven gears is adapted tomove proportionately to the differences in rotation between the mastercontrol shaft and the governed shaft. These movements of thedifferential housing are automatically transmitted to the throttle orother speed-com trol mechanism of the governed motor so as to speed upor slow down the motor and thus bring the gears of the differential intosynchronism.

If .desired, variable speed mechanism may be introduced between themaster motor and the master control shaft driven therefrom, whereby thegoverned motor or motors may be rotated at a different absolute speedfrom the master motor but still kept in relative synchronism therewith.75 Referring now in detail to the present preferred The motor maticallydetects and measures differences between the angular velocity of thestandard or master rotating body or motor and the body or motor to becontrolled. As embodied,

the unit synchronizing device comprises an epicyclic gear train,preferably arranged in the form of a bevel gear differential (Fig. 2)although a other forms of epicyclic gearing and differentials may beused. The arrangement of the difierential gearing is such that one gearrotates with or is driven from the master or standard rotating body, asecond gear being driven in the opposite direction from the body ormotor to be controlled, while a third'element of the gear train, inaccordance with the principles of differential gearing, normally idlesin mesh with the other two driven gears and moves proportionately to thedifferences in the angular-velocities thereof.

7 As shown in Fig. 2, the shaft 2 is rotatably mounted centrally of thecasing 3 of the unit synchronizing device, said shaft being driven fromor rotating proportionately to the standard or master rotating body ormotor. At the inner or free end of the shaft 2, is keyed a bevel gear 4so as to rotate with the shaft. At the other or left hand end of thecasing 3 is mounted a rotating shaft 5, preferably disposed parallel toand in line with shaft 2, and being driven from or rotatingproportionately to a motor or other rotating body to be controlled. Saidshaft 5 is mounted and driven to turn in the opposite direction fromshaft 2. A bevel gear 5 is keyed to the inner end of shaft 5, similarlyto gear 4.

As embodied, the bevel gears 4 and 6 form the active members of adifferential gear train, which in addition comprises the cooperatingidlers I and 8 which mesh with the upper and lower peripheriesrespectively of the gears 4 and 6. The idler gears l and 8 are mountedfor free rotation about'the vertical stub shaft 9, which is keyed to andforms a fixed partof the differential gearing housing l0.

The differential housing iil comprises an extending sleeve I l whichprojects to the left in Fig. 2 and forms a bearing for the shaft 5,which'rotates therein. The sleeve II in turn is rotatably supported inthe normally stationary casing-3 by bushing l2 formedon the left endthereof. A similar but longer sleeve l5 projects to the right in Fig. 2and forms a rotatable support for the master shaft 2. The sleeve I5 isin turn rotatably supported in the housing 3 at the right hand endthereof by the bushing i6, and is supported at an intermediate pointnear the right hand end of the differential housing llby bushing I!mounted in the intermediate web 3 of the housing 3.

It will be understood that, in accordance with the. principles ofoperation of differential gearing, so long as the gears 4 and 6 turn atequal angular velocities in opposite directions, the gears and thedifferential housing about gear 6 as a 4 will be compensated for by aturning of shaft 9 4o housing a.

pivot, and the amount of movement of the differential housing II] willbe proportional to said increment. If, on the other hand, the rotaryvelocity of shaft 5 exceeds that of shaft 2, the

5 housing III will turn proportionately to said difference but in theopposite direction.

Means are provided for utilizing the movements.

of the differential housing In to control the ro-" tation of shaft 5 orof the body or motor to be 10 controlled, whereby the said differencesin angular velocity of shafts 5 and 2 will be automatineed notnecessarily have a rotary motion. It is only necessary that the motionof such machine or motor be capable of transmitting rotary motion toshaft 5. For example, the machine to be controlled might be areciprocating engine, having shaft 5 driven by rotary connectionwith aflywheel or the like. 7

As embodied, the movement of differential housing l0 may be transmittedthrough the integral sleeve l5 to a control-rod or lever which isconnected to the throttleor speed-control mechanism of the motor orother mechanism to be governed. The present preferred mechanism foractuating control-rod 20 from the rotatable sleeve l5 comprises arectilinearly movable rack 2| which is slidably supported at 22 and 23in-suitable bushings set into the Rack 2| receives its motion fromrotatable sleeve |5 through the pinion rotatably mounted about sleeve l5at the inner end of bushing It, the teeth of said pinion normallymeshing with teeth 3| on the rack.

' '45 The rack 2| is connected to control-rod 20 for imparting movementthereto by means of a bell crank lever 35 pivotally mounted to thecasing 3 at 15 and having a pivoted connection with the end of rack 2|through the slot'3l and pin 38. 50 The end of rack 2| is forked at 39 toreceive the slotted 'end portion 31 of the bell crank 35. The other arm40 of the bell crank is pivotally connected to the end of control rod2|) by means of cooperating clutching. member driven by the.

sleeve I5 is provided for transmitting the rotation of sleeve |5 topinion 30. As embodied, a cylindrical collar is mounted about the sleevel5 to rotate therewith, but is slidable therealong, being connected tothe-sleeve l5 by the 7 spline 5| which cooperates with a suitable grooveinthe collar member 50.

The collar 50 is provided with a clutching face for engaging with thefrictional ring 45, said-face comprising the outer or right hand flangedportion 52 of the collar. 50. The inner or left hand end of the collar50 is similarly constructed, having a widened flange 53, the inner faceof which is adapted for clutching connection with the annular clutchingmember 54' which is fast to the outer or right hand face of the web I!of the easing 3. The purpose and operation of this construction will bedescribed in" detail hereinafter.

Means are provided for variably positioning the clutching collar 50 withrespect to sleeve l5. As embodied, a control lever 55 extends through aslot 56 in the upper surface of the casing 3 (Figs. 2 and 3) and issupported fortranslation with respect to the casing 3 on the'slidablerod 5'|, which rod is mounted for sliding movement at 58 and 59 in theend wall 60 and the web I! respectively of the casing 3. The rod 51passes through a suitable opening 6| in the enlarged portion 52 of thelever 55, being fixed with respect to said lever by a pin '63. The lowerend of the lever 55 is forked to form a yoke about the clutching collar50, the arms 64 of the yoke being slidably connected to the rotatablecollar 5|J by means of the grooved ring 55 which surrounds the-collar 50at the central portion thereof. The ring 55 is mounted to rotate withthe collar 5|! by means of pins 56 and 51 which extend through suitableopenings in the ring and are supported at their outer and inner endsrespectively in the flanges 52 andv 53 of the collar 50. The ring 65 isslidable along the rods 68 and 61, but is prevented from free slidingmovement by helical compression springs 68 and 69 which are positionedabout the pins 66 and 61 and bear against the faces of the ring 65 andthe inner faces of the flanges 52 and 53 respectively. The ring 65 isprovided. with a peripheral groove 10. Either arm 64 of the yoke onlever 55 is provided with an arcuate member H which rides in the groove10 and is fixed to the lower end of its arm 54. Thus translatorymovementof the lever 55 parallel to the axis of shaft 2 will carry the cpllar 50and its cooperating structure along sleeve I5 and into engagement withone or the other of the clutching faces 45. or 54.. Rotation of collar50 with respect to the ends of'the yoke 64 is permitted by the freerotary connection between the arcuate members II and the grooved ring10.

In the present embodiment. of the invention, the clutching member 50 hasthree alternative positions. As shown in Fig. 2, member 50 is located atan intermediate position on the sleeve I5, in which position there is nocontact with either of the clutching members 45 or 54. Movemen of thepositioning lever 55 to the right will carry the clutching mechanism 50along to the sleeve l5 and into driving contact with the pin-..

ion 3|], while movement of the lever 55 to the left will carry theclutching face of flange 53 into frictional clutching contact with themember 54.

Inthe following description, the right hand or driving position of theclutch will be designated as the .governing position; the left handsetting of the clutch as its locked position; and the intermediate orfreely rotating position shown in Fig. 2 will be called the neutralposition.

Means are provided for locking the clutching mechanism 50 in any one. ofthe three positions enumerated above. Any known or suitable mechanismmay be used for this purpose, the means shown comprising aspring-pressed dog 15 pivotally mounted on the handle of lever 55, andadapted to cooperate with the locking grooves 15, TI and 18 in the plate19 on'the top of the casing 3 for holding the clutch in the locked,

neutral or governing positions respectively. It will be noted that thesprings 68 and 69 serve the usual function of a spring clutch inpermitting gradual increase. of clutching pressure between the clutchfaces, so that when the lever is locked in one of the notches Hi or 18,the cooperating springs 69 or B8 are under compression. These springsalso act to center the clutch and tend to return it'to neutral.

It will be clear from the foregoing description that when the clutch-Ois in the right hand or governing position, any motion of thedifferential housing I0, resulting from differences in angular velocityof the shafts land 5, will be automatically transmitted 'to the pinion30 and rack 2| and through them to the throttle-control rod 20;

Referring now to those features of the invention for automaticallycontrolling the angular velocity of a rotating body, such as a gasolinemotor, and for maintaining the same in synchronous rotation with astandard rotating body or master motor, such use of the unitsynchronizing device will be described in connection with thesynchronous control of an airplane motor, although it will be understoodthat the invention is by no means limited to such use and is broadlyapplicable to many other types of mechanisms, the following descriptionbeing merely by way of illustration and example. Referring to Fig. 1,the motors A, B and C of a tri-motor airplane are diagrammaticallyindicated, each motor being shown with its propeller in directconnection with the motor shaft; For the present description we willlimit our consideration to motors B and A, assuming that B is the mastermotor and A the motor to be controlled and automatically main tained insynchronous rotation with the master motor B. I

In accordance with the invention, the throttle of motor A is to beautomatically controlled by a unit synchronizing device so as toautomatically speed up or slow down motor A and thereby eliminatedifferences between the velocity thereof and that of master-motor B. Asembodied, a shaft 5a is provided extending from motor A and being drivenpreferably directly from the main shaft thereof.

The shaft 5a is connected to a unit synchronizing device Ia, which issimilar in construction and operation to the unit synchronizing device Ialreadydescribed in connection with the mechanisms shown in Figs. 2 and3. It will be understood that the parts in .Fig. 1 marked with the samereference, numerals as those used in describing the unit synchronizingdevice, but bearing the lettered suffix (la, la, etc.) indicate partspertaining to motors A, B and C, but having the general constructionsand operations of the similarly numbered parts of the unit synchronizingdevice already described. 4 v

A shaft 2a is driven from the master motor B so as to rotateproportionately to the rotary velocity thereof and in the oppositedirection from shaft 5a. As shown, shaft 2a is driven by bevel gearing80a from shaft Bla which is connected for direct driving from shaft 21).Shaft 2b is preferably driven from the main shaft-of master motor B. Forpurposes of the present description, the driving connection D actuallyshown between shaft 21) and Bid should be disregarded and it should beassumed that the driving connection from shaft 2b to Bid is a directdriving connection, such as a l to 1 bevel gearing similar to 80a.

The unit synchronizing device la is, provided with the rack 2|a, whichis connected by bell crank 35a. to the throttle control rod 200, formotor A. As shown, control rod 20a is connected to the throttle 85a ofmotor A so as to directly move the same proportionately to the movementof rack Ho and thus transmit the motion of the differential housingincorporated in the unit synchronizing device la to the throttle ofmotor A.

The motor C may be similarly synchronized with the master motor B, theembodied mechanism comprising the unit synchronizing or control shaft8lc driven from the master control shaft 211, and driving directly theshaft 20 which is connected in the manner hereinbefore described withthe gearing-of the unit synchronizing device lc. Shaft 50 is driven frommotor C and connected to the unit device lo, the parts 2| c, 200 and 850being constructed and operated in a manner identical with thecorrespondingly indicated parts of the mechanism for motor A.-

Master motor B may be provided with a manually controlled throttle,pivoted lever 9|] being attached to control-rod 9|, which is connectedto the throttle 85b of motor B.

It will be understood that the number of motors controlled by andsynchronized with the master motor B is not limited to the two motors Aand C shown. The unit control shafts Ila and/or 8 lo may be extended andas many motors attached thereto and controlled thereby as may bedesired. Each motor so controlled would, of course, be provided with aunit synchronizing device constructed and connected to its respectivemotor to be controlled in the same manner as devicesla and lo.

It will further be understood that the master motor B need notnecessarily be a large or standard driving motor, although in the caseof a trimotor airplane or the like, one of the regular driving motorswill ordinarily be used for the master motor. However, for the purposesof my invention, the unit synchronizing shafts Ola and/or Bic couldequally well be driven by a small motor or other standard rotating bodywhich would be used solely or principally for the purposes ofsynchronous control.

The operation of the hereinbefore described mechanism may be brieflystated as follows:

Let it be assumed that unit control shafts Ma and Bio are driven atequal velocities from shaft 2b of motor B. Further, assume that theclutches of both unit synchronizing devices .Ia and lo are set in thegoverning position. With these settings, any difference in R. P. M.between shafts 5a and 2a will be instantly transmitted to the controlrackjla of unit la andthrough said rack to the throttle of motor A. Thusif motor A is lagging and the R. P. M.,thereof is less than that ofmotor B, rack 2Ia will be moved to the right so as to advance thethrottle of motor A and'thus speed up the motor. As soon as synchronousrotation is achieved between shafts 5a and 2a, the movement of rack Zlawill automatically cease. If, on the other hand, motor A is turning atgreater R. P. M. than motor B, the

.unit synchronizing device will automatically motor B is advanced andthe speed thereof increased, the unit synchronizing devices [a and lowill automatically advance the throttles of their respective motors Aand C. In this way, an

automatic and synchronous controlof the speed of any desired number ofmotors can be obtained merely by the manual operation of thespeedcontrol or throttle of the master motor. Means are provided forthrowing out the synchronous control, and permitting one or more of themotors to run individually and independently of the master motor. Asembodied, the clutch mechanisms of the unit synchronizing devices laand/or It: may be set inthe intermediate or "neutral position. With theneutral settings, the differential housings of the unit synchronizingdevices will not transmit their movements to the racks Zlaand 2lc, sothat no movement will be transmitted to the throttles of motors A or C.As a result, any or all of the motors A, B and Y C may be runindependently of each other regardless of the respective differences inrotation of shafts 5a, 2b and 50.

In accordance with one feature of the invention, the relations of themaster motor and motor or motors under control thereof may beinterchangeable so that the master motor will be governed or controlledand one of the other motors will become the master motor. As embodied,the master motor B may be also provided with a unit synchronizingdevicelb which is connected in the usual manner to shaft 2b, the latterbeing formed in two parts and said parts connected by the differentialgearing of the unit synchronizing device lb. The throttle 85b of motor Bmay be provided with an alternative automatic control rod b, connectedto the control rack Zlb of the unit synchronizing device lb. When themaster motor shaft 2b is thus provided with a unit synchronizing devicelb. it is necessary that the clutch of said dev ce lb be set in the"locked" position in order that the motor B may operate as the mastermotor. The reason I 40 for this will be made clear byreferring to Fig. 2

- and assuming that the clutch mechanism 58 has been moved to the lefthand or locked position with the dog 15 set in notch 16' and the clutchface engaging the clutching ring 54. With such clutch setting, thedifferential housing II] will be locked and cannot turn. The result ofsuch looking will be that the shaft 5 (in the present example the upperportion of shaft 2b in Fig. 1) will trans-' mit its driving forcedirectly to shaft 2 (the lower portion of shaft 2b) turning said shaftat the same speed but in the opposite direction. In other words, theunit synchronizing device will operate as a simple reversing gear whenin the locked position.

It' will be understood that in the preferred or usual arrangement for amulti-motor installation. all motors will be provided with unitsynchronizing devices so that interchangeability in the relations ofmaster motor and controlled motors can 60 be accomplished simply byshifting the clutches on the unit synchronizing. devices of two or moremotors. In the example just described, where motor B is operating as themaster motor and the r clutch of unit synchronizing device lb is in thelocked position, the lower portion of shaft 2b will turn at the'same R.P. 'M. as the upper portion, but in the opposite direction. In order toimpart the proper direction of turning to shafts 70 2a and 20, sothatmotors A, B and C will all drive in the same direction, thebevelgearings 80a and 801) would be reversed in their settings on shafts 5 ofturning of shafts flla and M0 wouldbe those chronizing device la.

shown by the dotted arrows, due. to the reversed drive from the lowerportion of shaft 2b.

If it is desired that motor A, for example. be set to operate as. themaster motor and motors B and C be controlled thereby, the clutch ofsynchronizing device lb will be set in the governing position andthe'clutch of device In. will be set in the locked position, therebymaking the drive of shafts Bio. and Bio come from shaft 2a of motor A.When motor B is set to operate as a controlled motor, the throttlethereof will be actuated automatically by rack 2lb and controlrod 20b.

Means are provided for indicating, visually or otherwise, the relativedifferences in rotation between a motor being controlled and the mastermotor or other rotating standard. As embodied, the motion of thedifferential housing ll! of a unit synchronizing device (Fig. 2) may beutilized to indicate the actual differences in synchronism between themaster motor and the motor to be controlled. For this purpose, a spurgear 90 may be keyed to the rotatable sleeve ll of the diiferentialhousing l0, said gear being positioned between the left hand end of thedifferential housing Ill and the end wall 9| of easing 3. An indicatorshaft 92 is rotatably mounted in said. end wall Bl above. and parallelto shaft 5, and is driven by spur gear 90 through the pinion 93 keyed tothe inner end of shaft 92.

Means are provided for visually indicating the amount and direction ofrotation of shaft 92 to thereby indicate the differences in rotaryvelocity between the motor to be controlled and the master motor. Asshown. in Fig 1, a visual indicating device 9311 is connected to shaft92a of .unit synchronizing device la, the connection preferably beingmade by means of a flexible shaft 94a or similar suitable mechanism fortransmitting the motion of the shaft BZa-to the indicating device,regardless of where the latter may be located.

The visual indicating device 93w, which for convenience of=nomenclaturemay be hereinafter called a synehro-indicator", may be of any suitableor known construction forthe purposes to be accomplished. For example,the synchro-indieator'may be an ordinary pointer and dial which willmeasure, and indicate the amount of rotation of the differential housingof the unit syn- If the pointer remains stationary, it would indicatethat motor A and motor B were in synchronism, while the difference insynchronism would be indicated by the speed at which the pointer turned.Clockwise motion of the pointer would indicate that motorA was rotatingfaster than motor 3 while counterclockwise motion would indicate thereverse. This could be accomplished, for example, by using a magnetictype speedometer for indicating both right and left positions over ascale having zero in the center, right signifying slow and left fast orvice versa, the graduations to read revolutions indicating device, theimportant feature being that indication is automatically made of theactual differences in R. P. M. of the two. motors connected to the unitsynchronizing device.

In certain cases it may be desirable to utilize the principles of myinvention solely for the purpose of indicating differences in R..P. M.of rotating bodies. In such case the unit synchronizing device could beset in the neutral position and the sole function of the device wouldthenbe to actuate the synchro-indicator pointer. Such in position.morethan the usual opposition in its movement indication could be usedby the operator for manually controlling and synchronizing the motors.On the other hand, the synchro-indicator will also operate whileautomatic governing of the motor A is taking place through the controlof the throttle by the unit synchronizing device Means are provided i orrendering the synchroindicator non-recording. As embodied, a clutch 950.may be provided in the drive of the synchroindicator 93a. fordetachingthe same from the drive of shaft 92a. With this clutch disconnected, theunit synchronizing device would continue to control the throttle ofmotor A (assuming the device to be set in the governing position) whileno indication would be made by the synchroindicator.

In accordance with one feature of the invention, safe-guards areprovided for preventing harmful or continued automatic operation of themotor-control devices in the event of abnormal or accidental occurrencesin the operation of the system. For example, theinvention providesdevices for preventing undue movement of the throttle of a governedmotor in the event that such motor goes dead while being controlledauto? 'matically from the master motor. Referring for the sake ofillustration to motors A and B, when B is the master motor throttle 85aof motor A is automatically moved to accelerate motor A whenever the R.P. M. thereof falls below that of the motor B. Normally the lack ofsynchronization between motors A and B will be relatively slight andquickly corrected so that the movements of the throttle 850. willusually be of little magnitude. However, if motor A suddenly stalls, theautomatic operation of unit synchronizing device Ia. would operate tothrow the throttle 850.

wide open and would continue to force the rack 2|a. and the throttlecontrol rod 200. in the throttle-opening direction.

The invention provides mechanism for preventing movement, of thethrottle beyond its normal limits of opening and closing. As embodied,the throttle-control rod 20 (Fig. 3) is connected to the end 40 of bellcrank 35 by a sleeve 4| provided with a socket 96 which rewives andsupports the end of rod 20, which normally stops short of the right handend of the socket. Rod 20 is releasably held in its normal position insleeve 4| by a spring pressed ball and socket device 91. For all normalmovements of rod 20 in controlling a motor throttle, the spring pressedball device 51 will sufiice to hold rod 20 However, if the rod 20encounters (as when the governed motor stalls and the throttle has beenmoved to its outer limit) the rod 20 will slide over the ball and permitfurther movement of the bell crank in either direction.

Additional safe-guard means are provided for preventing undue orabnormal movement of the control rack 2| of the unit synchronizingdevice. For example, in the case of a stalled motor, it is desirablethat the rack Zia be disconnected from the driving action of thedifferential housing when or soon after the throttle control-rod 20 hasreached the limit of its motion. As embodied, the rack 2| is providedwith a limited number of gearteeth 3|. disposed near its central portion(Fig. 4) On either side of .the teeth 3| the rod is provided mutilatedportions 98 and 99, so that movement of the rod beyond the teeth 3| willdisconnect the rod from the drive of the pinion 3|].

For maintaining the gear teeth 3| of the rack ratio.

in register with the pinion 3.,- the lower end of rack 2| is provided'with notches 26 and 21 which are spaced apart a distance substantiallyequal to that of the range of the gear teeth 3|. A spring-seated lockingball 28 is maintained against the'surface of rack II and isadaptcd toconstruction undue movement of. the rack be-' yond the range of theteeth 3| is prevented. so that as soon as the teeth 3| are thrown beyondthe driving contact of the pinion 30. so that there can be no furtheractuation of the rack, the rack will stop and register and re-engagementof the pinion teeth will be easily effected.

While the hereinbeiore described safety guard mechanisms have beenmentioned in relation to the operation of the system in the event thatthe governed motor stalls, it will be understood that these devices alsooperate to prevent malfunctioning of the system in the event that themaster motor stalls. For example, the rack 2| is provided with mutilatedportions on either side of the centrally disposed teeth 3| so that unduemovement of the differential housing ID in either direction will berendered harmless.

In some cases it may be desirable to utilize the means for throwing oneor another of the clutches of the unit synchronizing devices to theneutral position, for example, in the case of a stalled motor or thelike. Thus, assume that the master motor B fails or becomesincapacitated and it is desired to stop it and to substitute the motor Aas the master motor for governing the motor C. This may readily. beeffected by placing the device lb in neutral position and the device lain locked position, whereupon the motor B may be stopped and the motor Awill serve as a master motor to govern the motor C.

In accordance with one feature of the invention, means are provided forvarying the ratio of rotary velocities of the diiferent motors to thatof themaster motor, while maintaining relative synchronous rotation ofall motors. In the foregoing description, the assumption'has always beenmade that the absolute rotary velocity of motors A and C should bemaintained the same as that of motor B, i. e. a. 1 to 1 speed However,in many cases it would be desirable to drive motor A and/or motor C at adiiierent actual speed from that of motor B, while maintaining motors Aand C in relative synchronism with the master motor B. In the case of atri-motor airplane, for example, it is frequently desirable to vary therelative velocities of motors A and C while maintaining them in relativesynchronism with the master motor B and with each other. An example ofsuch a case would be in making a banking turn of an airplane. Assumingthat motor A is the left hand motor of the plane, and the turn is to. be

mechanism D is provided between the mastermotor and the control devicesfor the motors to be governed. In accordance with the broad principlesof the invention, the variable speed mechanism may comprise any known orsuitable device :for selectively varying the speed ratio of the shaftsOla, 2a and/or lie and 20 with respect to the speed of motor B astransmitted by shaft 2b.

A simple form of such mechanism is shown in Fig. 1, comprising themechanism marked D therein. As embodied, the lower end of shaft 2b isprovided with a circular disc I (Figs. 1, and

7), the lower face thereof being covered with 5 friction material IOI.Driving force is transmitted from the disc I00 separately to-shafts 8Iaand M0, each of said shafts being provided at its end with africtionally driven roller I 02a and I020, respectively. Means fortransmitting driving force to the rollers I02a and I020, comprisesfriction rollers I030. and I030, interposed between the friction surfaceof disc I00 and the rollers IIl2a and I020, respectively. As shown inFigs. 1, 5 and 7, rollers W311 and I030 are rotatably mounted on thenon-rotatable shaft I04, the ends of which are supported. by the endwalls I05 and I06 of the casing D for the variable speed device. Therollers I020, and I02c'are fixed to the ends of shafts 8Ia and tilerespectively, the surfaces of said rollers being preferably composed ofleather or other friction material. Shaft Bla is rotatably supported inthe end wall I06 of casing D by the bushing I01, while the inner end ofshaft 8 la is supported for rotation in the bushing I08 formed in theintermediate web I09 of the casing D. Shaft BIc is similarly supportedby bushing H0 in wall I05 of the casing, the inner end of shaft 8I0being supported likewise by bushing I08. a

The friction disc I00, which is keyed to the lower end of shaft 2b, ispressed into yielding frictional engagement with the tops of rollersI03a and I030 by the helical spring II5 which surrounds the lower end ofshaft 22) and presses against the lower face of the ball-bearing raceII6. This'race II6 supports the ball-bearings interposed between thespring and the lower face of collar II1 formed in the upper portionofcas ing D and surrounding the shaft 2b.

It will be clear from the foregoing that independent driving motion istransmitted from the faceof friction disc I00 to rollers I03a and I030and through them to rollers I020. and I020 respectively, therebyindependently driving shafts 8Ia and 8I0 from the master motor. "Therotary velocity imparted to roller I03a, for example, by disc I 00 willdepend upon the radial distance of the roller from the center of the.

o0 thereto by splines I20 and I2I, which nevertheless permitlongitudinal movement of the shaft. The end of shaft I04 is pivotallyconnected to a control rod I23 which in turn is linked to a controllinglever I22, whereby movement of the lever will move roller I03a nearer tothe center of the disc and roller I030 farther. from the center thereofor vice versa Additional means are provided for varying the relativepositions'of rollers IBM and Ill3c'with respect to'disc I00independently of the movement of shaft I04. As embodied, these rollers Vare actually mounted on a hollow sleeve I 25 'which surrounds the lefthand portion of shaft I04 and is slidable with respect thereto, thespline I2I 15 being actually set in said sleeve. Rollers I0'3a and Miaare normally fixed longitudinally of the sleeve by suitable collars I20and I2! which are held in position by set-screws I28, the rollers beingpreferably mounted onball-bearings I29 set in suitable supporting ringsI30 on the sleeve I25.

Sleeve I25 is provided with mechanism for varying the longitudinalposition thereof with respect to shaft I04, comprising a hexagonalscrew-threaded cap I35 which is made fast to the end of sleeve I25 by abolt I36 screwed through .the side of the cap and projecting into acircular slot I31 in the sleeve. The left hand end of shaft I04 isscrew-threaded as at I38, so'that turning movement of cap I35 aboutshaft I04 will move the cap-and the sleeve I25 axially of the shaft, itbeing understood that the circular slot'l31 permits turning of the capI35 about the end of the sleeve.

The operation and functioning of the variable 1 such speed variation inthe motors is the making of a banking turn about motor A, in whichinstance it is desirable to slow down motor A and accelerate motor B.

By virtue of the mechanism hcreinbefore described, the pilot would beable to make the desired speed variations in motors A and B by atemporary setting of the speed-change device B through lever I22. Thatis, by moving lever I 22 to the right, rollers I 03a and I030 would heslid to the right the desired distance, thereby varying their radialpositions with respect to disc I00 and thus decreasing the speed of theformer and increasing the speed .of the latter. Consequently shafts 8Iaand 20 will slow down while shafts 8I0 and 20 will speed up acorresponding amount. The deceleration of shaft 2a will be transmittedto the throttle of motor A through the actuation of the unitsynchronizing device Ia and the motor will be slowed down, while acorresponding acceleration will be imparted to motor C.

It will be .clear that the deceleration and acceleration of motors A andC,- respectively, will take place independently of the actual speed ofmotor B which will continue to run at the speed determined byitsthrottle setting. As soon as the banking movement has been completed,the pilot' may return the, lever I22 to its normal or central settingand normal synchronized driving of the three motors will be resumed. Itis obvious, of course, that the pilot mayvary the positioning of leverI22 and the setting of the variable speed device D- during the bankingmovcment of the plane so as to govern the relative speed variations ofthe motors as nicely as de sired. For automaticoperation of the speedvariations in banking", it may be desirable to connect the lever 122 orits equivalent to the joy stick" or other device for. controlling theposition of the ailerons.

-In many instances, particularly in the control of an airplane, it maybe desirable to permanentlyor semi-permanently drive one or more of thegoverned motors at an increased or decreased speed ratio with respect tothe master motor or the other governed motors, while maintainingrelative synchronism with the master motor. In the case of the airplane,for example, the gyroscopic moment of the propellers, or other inherentforces, may induce a. turning moment of the entire airplane to the rightor left. To correct this, it would ,be desirable to always drive theright hand motor at slightly different speed from the left hand motor;By initially setting the rollers H1311 and I031: along the shaft 10 I04,by means of the screw-threaded adjustment of sleeve I25, it is possibleto make a permanent or semi-permanent adjustment of the ratio of Isynchronization between the master motor and the motors A and C. Such anadjustment would normally be made independently of the temporary settingof lever I22, for the purpose of trueing ship" or any other desiredrelative variation in themotor speeds.

It will be understood that neither of the speed variations describedaffects thespeed of the center or master motor B, but only the relativeratio of synchronization between the master motor and the motor ormotors being governed. In

other words, the speed of the master motor is dependent solely upon themanual throttle control,

while the speeds of the governed motors can be kept in a direct l to 1ratio with that of the master motor or may be varied relatively theretoso as to get any desired speed ratio while maintaining automaticsynchronization.

In certain cases, it might be desirable to vary the ratios ofsynchronization between one of the governed motors and the master motorindepende'ntly of the other governed motors. This could 5 beaccomplished by making the rollers Ba and lll3c independently slidablealong sleeve I25 or shaft, I so that the movement of one roller wouldnot necessarily affect the positioning of the other with respect to thefriction disc I00. ,40 Such a mechanism would be used in case it weredesired to maintain motor C, for example, at the l to 1 ratio with themaster motor B while driving motor A at a different ratio ofsynchronization. For the sake of clearness, no mechanism forindependently varying the positions of rollers l03a and "Be along sleeveI25 has been shown, but it will be understood that means for effectingsuch variation and functions of such independent variations are withinthe scope of and are contemplated by my invention.

7 The invention inits broader aspects is not limited to the specificmechanisms shown and described but departures may be made therefromwithin the scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chiefadvantages. a

What I claimis: 1. A mechanism forsynchronous motor control 6'0including in combination a master motor, a governed motor, means formaintaining the governed motor rotating at the same or a multiple of thespeed of the master'motor, and means for varying the speed ratio betweenthe master motor and governed motor while maintaining the gov- 1 trolincluding in combination a master motor, a

plurality of governed motors, means for maintaining the governed motorsin synchronous rotation with the master motor, and means for varying thespeed ratios of the governed motors with respect to each other whilemaintaining the governing action between the master motor and thegoverned motors.

4. A motor control system including in combination a plurality ofmotors, one of which is manually controllable, differential governingde-- vices connecting the other motors with the manually controlledmotor to maintain predetermined relationships between the angular speedof the manually controlled motor and the other motors, and means forselectively varying the speeds of the governed motors relative to eachother.

5. A motor control system including in combination a plurality ofmotors, one of which is manually controllable, differential governingdevices connecting the other motors with the manually controlled motorto maintain predetermined relationships between the angular speed ofthe, manually controlled motor and the other motors, and manuallyoperable, mechanical means for selectively varying the speeds of thegoverned motors relative to eachother.

6. A motor control system including in combination a tri-motoredaircraft, means for manually controlling the speed of one of the motors,means for automatically maintaining the speeds of theother motorsproportionate to that of the manually controlled motor, and meansadapted to be controlled by the steering mechanism of the aircraft forautomatically varying the speeds of certain of said motors with respectto each other.

7. A motor control system for a multi-motored vehicle including incombination a manually controlled motor, a plurality of other motors,means for automatically maintaining the other motors at the same angularspeed as the manually controlled motor, and means for selectivelyvarying the relative speeds of said motors without interfering with saidautomatic means.

8. Amotor control system for a multi-motored aircraft including incombination a plurality of propelling motors in an aircraft, meansformaintaining the angular speeds of said motors equal or proportional toeach other, means for increasing the speed of one of the motors andmeans for automatically decreasing the speed of another motor aproportionate amount.

9. A motor control-system for a multi-motored nism of the aircraft forautomatically varying the proportionate speeds of said motors.

10. -A motor control system for a multi-motored aircraft including incombinationa tri-motored aircraft, means for manually controlling thespeed of a center motor, means for automatically varying the speeds ofthe outlying motors proportionately to-changes in the speed of thecenter motor, and means for independently varying the speeds of theoutlying motors with respect to each other to assist in steering'theaircraft.

11. A motor control system for a multi-motored vehicle including incombination a master motor, a governed motor, means for varying thespeed of the master motor, governing means for imparting correspondingspeed variations to the governed motor, and means for interchanging therelation of the motors'whereby the original master motor may be governedby the other motor.

12. A motor control system for a multi-motored vehicle including incombination a master motor, a governed motor, means for varying thespeed of the master motor, governing means for imparting correspondingspeed variations to the governed motor, and means for interchanging therelation of the motors whereby the original master motor may be governedby'the other, mo-

tor, and means for optionally rendering said mo- 1 tors independent ofeach other.

13. A motor control system for a multi-motored vehicle including incombination, a master motor, a plurality of governed motors, means forvarying the speed of the master motor, governing means for impartingcorresponding speed variations to the governed motors, and means forinterchanging the relation of the motors whereby one of the previouslygoverned motors becomes a master motor to govern the speed of at leastone of the previously governed motors.

of motors.

15. A motor control for a multi-motored aeroplane including incombination a plurality of motors including a master motor and governedmotors, governing means for imparting corresponding speed variationsunder the control of the master motor to at least one of the governedmotors, means for varying the speed of the motor which acts as themaster motor, means for interchanging the relation of the governingmeans with respect to the motors whereby a previously governed motor maybe adapted to act as a master motor for governing at least one of theplurality of motors.

16. A motor control system for a multi-motored aeroplane including aplurality of motors, including master and governed motors, governingmeans selectively inter-relatable with said motors for impartingcorresponding speed variations to a governed motor from the motor whichacts as a master motor, said selectable interrelatable governing meansalso adapting different motors of the plurality of motors to act as amaster motor, and means for varying the speed of the motor which acts asa master motor.

7 17. A motor control system for a multi-motored aeroplane including aplurality of motors, including master and governed motors, governingmeans selectively inter-relatable with said motors for impartingcorresponding speed variations to a governed motor from the motor whichacts as a master motor, said selectable inter-relatable governing meansalso adapting different motors of the plurality of motors to'act as amaster motor, and means for varyingthe speed of the motor which acts asa master motor, and means for selectively disabling any stalled motorand disassociating it from governing relation with the remaining motors.

GRAYSON SCHMIDT.

